It has to seal well and it would need new filters. Filters degrade over time. Can you get new filters for it?
You can test the seal by donning the mask, then tightly cover the inlet or inlets with the palm of your hand or both hands if there are two inlets. Then inhale as hard as you can and hold your breath.
If the mask sucks tight up to your face and doesn't move when you hold your breath, you are getting a good seal. If the mask slowly moves away from your face as you hold your breath, the seal is not good enough.
I put it on and it seals. Everything about this mask is in mint new shape but it's the effectiveness of the canister that would be in question. So I guess it wouldn't work. I can't get new filters for it. I just though it might still be good since it was made in america when america was america!